Water is the principal cause of distress in many types of structures. Geotechnical engineers and others skilled in the art specify and purchase sand, stone, or gravel as drainage means for conveying fluids to collection pipes. For some years, geocomposite materials have been used to complement natural earthen materials. Typically, such geocomposites are manufactured with a rigid core element encased between permeable non-woven fabrics that are thermally bonded to the rigid core element, or woven fabrics that are adhesively bound to the core element.
In conventional drainage laminates, membranes or woven textiles are typically adhered to a core element, the core element having voids or channels which permit the flow of fluids in a desired direction, typically away from the structure. However, the adhesions between the core element and the membrane or textile often fail in conventional laminates, resulting in intrusion of the membrane or textile into void spaces and the consequent clogging of those voids. With sufficient intrusion into the voids, clogging of the voids occurs, and insufficient drainage is provided to the structure with which the conventional laminate is associated. Such insufficiency often leads to failure of the structure or to a significant reduction in the length of its useful life.
Similar clogging problems exist with respect to the use of laminates formed of a core element and a non-woven geotextile. Typically, non-woven textiles resemble sheet-like pads of random fibers. Because of this, they have numerous potential fibrous attachment sites that are available for adhering or bonding the non-woven textile to a core element. However, because the pore size of non-woven geotextiles is not uniform, and because their random fibers tend to trap various sizes of particles, laminates which utilize them often clog quickly. With the use of semi-permeable or impermeable membranes, however, other problems exist. Because such semi-permeable or impermeable membranes are usually quite smooth, they are difficult to bond to core elements whether such bonding is effected by adhesives, heat fusion, laser welding or by ultrasonic bonding techniques. As a consequence of this, the adhesion between a membrane and its adjacent core element often fail in use.
The problems with the existing synthetic drainage technologies are therefore numerous. This is so because many synthetic drainage technology applications do not provide laminates that yield acceptable performance characteristics while retaining a reasonable amount of bond or adhesion between layers of the geocomposite. For example, even though leachate collection systems are more suitable for woven geofabric laminates, the geocomposite structures that use woven fabrics are limited in their use to those installations that allow for chemical adhesives to produce the bond between the core element and the fabric. These adhesives are typically soluble or degradable, and therefore fail to retain acceptable bonding characteristics over time. A related problem pertains to the fact that the bond strength of chemical adhesion is less than bonds provided by thermal methods such as heat fusion or laser welding.
Moreover, many specifiers are reluctant to introduce additional chemical constituents, such as are found in adhesives, into environmental applications. Moreover, conventional woven products cannot be thermally bonded to a degree that is acceptably effective for the areas or milieu of intended use. These disadvantages exist, at least partially, because woven fabrics are produced with a paucity of effective adhesion or bonding sites, that is, few fibers or protrusions that extend from the surface of the weave. This means that few fibers are available for inter-laminar bonding such as would otherwise take place during lamination or co-extrusion with the molten form of a rigid core element or layer.
Similar problems exist with respect to non-woven geofabrics. In sum, no woven or non-woven geoproducts are currently produced that yield acceptable bonding or adhesion performance characteristics with respect to thermal lamination methods such as heat fusion, laser welding or ultrasonic welding. Because of the above-described problems, there is thus a need for geocomposite laminates having superior structural integrity with respect to the maintenance of void spaces over time. More specifically, there is a need for geocomposites having superior bond strength between the respective layers of the laminates.